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Neurocognitive Disorders
21
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21.1 Introduction and
Overview
Advances in molecular biology diagnostic techniques and medi-
cation management have significantly improved the ability to rec-
ognize and treat cognitive disorders. Cognition includes memory,
language, orientation, judgment, conducting interpersonal rela-
tionships, performing actions (praxis), and problem solving. Cog-
nitive disorders reflect disruption in one or more of these domains
and are frequently complicated by behavioral symptoms. Cogni-
tive disorders exemplify the complex interface among neurology,
medicine, and psychiatry in that medical or neurological condi-
tions often lead to cognitive disorders that, in turn, are associated
with behavioral symptoms. It can be argued that of all psychiatric
conditions, cognitive disorders best demonstrate how biological
insults result in behavioral symptomatology. The clinician must
carefully assess the history and context of the presentation of
these disorders before arriving at a diagnosis and treatment plan.
This century-old distinction between organic and functional
disorders is outdated and has been deleted from the nomencla-
ture. Every psychiatric disorder has an organic (i.e., biological or
chemical) component. Because of this reassessment, the concept
of functional disorders has been determined to be misleading,
and the term
functional
and its historical opposite,
organic,
are
no longer used in the current
Diagnostic and Statistical Manual
of Mental Disorders
(DSM) nomenclature. A further indication
that the dichotomy is no longer valid is the revival of the term
neuropsychiatry,
which emphasizes the somatic substructure on
which mental operations and emotions are based; it is concerned
with the psychopathological accompaniments of brain dysfunc-
tion as observed in seizure disorders, for example. Neuropsychi-
atry focuses on the psychiatric aspects of neurological disorders
and the role of brain dysfunction in psychiatric disorders.
Cognitive disorders tend to defy Occam’s razor, challeng-
ing clinicians and nosologists with multiplicity, comorbidity,
and unclear boundaries. These concerns are most true in elderly
adults, the demographic group most at risk for cognitive disor-
ders. Dementias of late life are particularly problematic in this
regard. Existing, although often unrecognized, dementia is a
major risk factor for superimposed delirium. Moreover, certain
dementias, such as dementia with Lewy bodies or late stages
of Alzheimer’s disease, may have chronic clinical presentations
virtually indistinguishable from delirium except for temporal
onset and the lack of an identifiable acute source. Similarly, the
course of nearly all subjects developing a progressive dementia
is complicated by the onset of one or more distinct behavioral
syndromes, including anxiety, depression, sleep problems, psy-
chosis, and aggression. These symptoms can be as distressing
and disabling as the primary cognitive disorder. Some of these
behavioral syndromes, such as psychosis, may themselves result
from independent underlying biologies and may be additive
with the primary neurodegenerative process.
The boundaries between types of dementia and between
dementia and normal aging can be similarly diffuse. Neuro-
pathologic studies of both clinical and population samples have
revealed a surprising truth. The most common neuropatho-
logic presentation associated with dementia reveal mixtures
of Alzheimer’s disease, vascular, and Lewy body pathologies.
Pure syndromes are relatively less common, although often the
dementia is ascribed to one of the coexisting pathologies. Strate-
gies regarding how to understand or reconcile multiple patholo-
gies in the clinic are needed, although they lag behind.
Definition
Delirium
Delirium
is marked by short-term confusion and changes in
cognition. There are four subcategories based on several causes:
(1) general medical condition (e.g., infection), (2) substance
induced (e.g., cocaine, opioids, phencyclidine [PCP]), (3) mul-
tiple causes (e.g., head trauma and kidney disease), and (4)
other or multiple etiologies (e.g., sleep deprivation, mediation).
Delirium is discussed in Section 21.2.
Dementia (Major Neurocogntive Disorder)
Dementia,
also referred to as major neurocognitive disorder in
the fifth edition of DSM (DSM-5), is marked by severe impair-
ment in memory, judgment, orientation, and cognition. The
subcategories are (1) dementia of the Alzheimer’s type, which
usually occurs in persons older than 65 years of age and is mani-
fested by progressive intellectual disorientation and dementia,
delusions, or depression; (2) vascular dementia, caused by ves-
sel thrombosis or hemorrhage; (3) human immunodeficiency
virus (HIV) disease; (4) head trauma; (5) Pick’s disease or
frontotemporal lobar degeneration; (6) Prion disease such as
Creutzfeldt-Jakob disease, which is caused by a slow-growing
transmittable virus); (7) substance induced, caused by toxin or
medication (e.g., gasoline fumes, atropine); (8) multiple etiolo-
gies; and (9) not specified (if cause is unknown).
In DSM-5, a less severe form of dementia called mild neuro-
cognitive disorder is listed. Dementia is discussed in Section 21.3.
